Improvement in artificial horizon tor sextants



J.A.ROGE RS..

Horizon for Sextants.

' Paten tedApri|12,1870.

' Connecticut, have invented a new and useful Arti- 'does not act injuriously on the materials of which'the diluted with a small proportion of strong alcohol.

. motion of the yoke, in a dircctionfi'om that axis at right angles to the direction of the-center of the float the yoke is made adjustable by proper means. By the timed elm strut dlliljlirr;

JOSEPH A. ROGERS, OF NEW HAVEN, CONNECTICUT.

Letters Patent No. 101,919, dated 4 mm, 1870.

' The Schedule referred mm these Letters Patent and making part of the same.

To all wlwm it may ccacem Be its-known that I,-Josn1=n A. Rooms, of New Haven, in the county of New Haven and State of ficial Horizon; and I do hereby declare that the following is a full, clear, and exact descriptionu of the construction and operation of the same, referenee' being had by letters to. the annexed drawing making a part of this specification, which is an isometrical representation of the' instrument, a central vertical section of theouter part or case having been made, for the purpose of exhibiting the interior parts,

The metallic cylinder A, intersected at right angles in its lower part by the smaller cylinder 0 D, forms a use which is completely filled with a suitable transparent liquid. For this purpose, almost any liquid may be employed which is quite transparent, and which instrument is composed, but I prefer to use glycerine The ends of this case, one of which is shown at B, are made of thin metal, and corrugated to accommodate the varying volume of the inclosed liquid corresponding to different temperatures, One end of the smaller cylinder 0 D is closed, and the other covered .by the plane glass E, care being taken to make a close joint between the glass and metal, so as to prevent the escape of the liquid.

From the closed end 0 a small tube, F, projects a short distance into the interior of the case, closed at its inner end by the plane glass'I, burnished in or otherwise secured, so as to prevent leakage.

At H is an aperture for introducing'the liquid which is afierward closed by a screw-plug.

The parts described above areshowu in section in the drawing. g

A piece, G G, secured to the inside of the case, sup: ports the cross K, which turns on pivots oiknife edges about an axis parallel to and a little below the axis of the short tube. I

' The cross supports the yoke L, which turns on pivots or knife-edges about an axis perpendicular to the axis of motion of the cross, and which axis, when horizontal, intersects the axis .of the short tube at right angles. The arrangement of. the cross and yoke is such that the latter has a limited motion of rotation in any direction without obstructing the .vicw through the tube.

A hollow float, M, of glass or thin metal, is attached to the yoke which-is kept vertical by its buoyancy.

The sight-vane N is also attached to tlie'yoke, one of its edges being straight and parallel to the axis of from the same axis, The distance of the vane from action 0! the float, the straight edge of the vane is kept constantly in'the horizontal plane passing through the axis of motion of the yoke.

A curved spring, Q, attached to the upper part of the case, limits the movement of the float, and prevents the vane from coming in contact with the case.

The sight-vane is viewed through theconverging lens 0, mounted in the ring I, which slides in or screws into'the tube F, to permit adjustment to the position of distinct vision.

A small piece, S, secured within the case, has a straight edge which is seen through the lens'parallel to the straight edge of the vane, when the axis of the case is horizontal.

The instrument may be attached to any apparatus with which it is to be used, by means of three lug: one of which is seen at R. -v

When the instrument described above is placed so that the axes of the cylindrical parts of the case are horizontal, the straight edge of the sight-vane will be seen through the lens, either with or without a telcscope, in the direction of the rational horizon. But if these axes deviate --somewhat from the horizontal, the straight edge will still be seen in the same direction, any small displacement of the axis of the lens from the horizontal plane containing the straight edge and the axis of motion of the float being very nearly compensated by the efiect of refraction at the surface of the liquid when the sight-vane and lens are placed atproper distances from the axis of motion of the float. These distances depend on the index of refraction of the liquid employed, and the focal length of the lens. They may be determined in any given case by the 'applicationof Well-established principles of optics, and their adjustment perfected by trial.

When this artificial horizon is attached to a sexmin; or other instrument held in the hand, the liquid alsd serves to check the vibrations of the sight-vane, the stability of which is further promoted by making altl) the parts connected with the float as light as possi le. Y

The parallelism of the wine and the straight edge fixed to the case is at the same time atest of the verticality'of the plane of tliesextant.

It is not, in general, necessarythat the apparent di- .rection of the sight-vane shall be precisely that of the rational horizon since any constant angle between them may be determined by experiment,-and afterward applied as index error to all observations made with'the same instrument;

Instead, therefore, of placing the sight-vane and center of the float in directions from the axis of motion of the floatat right angles to each other, they may be fixed at any convenient angle, the principles of their operation remaining the same.

It may also be desirable in some cases to dispense with the plane glass I atthe inner end of the small tube F. The lens 0 may then be brought in contact with the liquid inclosed in the case, and fixed at the proper distance from the axis of motion of the float.-

What I claim as my invention, and desire to secure by Letters Patent, is-

1. The float M, having a sight vane or its equivalent'attaehed, the whole being so suspended in a transparent liquid inelosed in asuitable case, that the buoyancy of the float tends to bring the sight-vane to rest in some fixed and definite position with ref erence to the horizon,- substantially as and for the purpose described.

2. The construction of the ease for containing the transparent liquid and float of an artificial horizon, the

' same consisting of the intersecting cylinders A and O 1), provided with the lens 0 and transparent plate E, substantially in the manner. herein shown and described.

3. The spring Q, in combination with the float M and sight-vane N, arranged to operate substantially as and for the purpose set forth.

JOSEPH A. ROGERS. Witnesses E. J. Looms, CHAS. MoDnmro'rr. 

